The present invention relates generally to angle measuring or indicating instruments and more particularly to a dental measuring instrument for indicating the labial inclination of central and lateral incisor teeth of both the upper and lower jaw, or maxillary and mandibular jaw, respectively.
The angle formed by a tangent drawn to the anterior or labial surface of the incisor crowns to the perpendicular drawn to occlusal plane is known as labial inclination. Occlusal plane is that plane which connects the incisal or biting edge of a central incisor tooth to the occlusal or biting surfaces of the molar teeth. The measuring of the labial inclinations of the incisor teeth becomes particularly important to the dentist or orthodontist in determining when the esthetic and functional requirements of treatment have been achieved. A ten degree, 10.degree., difference between the inclination of the maxillary and mandibular central incisors is the goal of treatment, with a range of +5.degree. to +15.degree. for the maxillary central incisor and a range of -5.degree. to +5.degree. for the mandibular central incisor considered acceptable. The ideal goal for labial inclination in the maxillary central incisor is +10.degree.; and 0.degree. for the mandibular central incisor, and orthodontic treatment is directed, at least in part, to the attainment of these angular goals. The establishing of treatment goals for incisor inclination is related also to mathematical tooth size ratios as determined through the use of the Bolton Tooth Size Analysis, 1952.
Previously, the accepted method for determining labial inclination was to draw a tangent to the anterior or labial surfaces of the incisor teeth, whose labial surfaces were traced from a lateral cephalometric head x-ray film. Since superimposing problems exist with the cephalometric headfilm, and since the labial crown surface is not flat, but curved, the possibility of error is great. Also, the procedure requires periodic x-rays and tracings, which is time consuming, expensive, and subjects the patient to additional radiation.